Hospital Pauses Test of an Ebola Vaccine Licensed to Merck

A test of an experimental Ebola vaccine recently licensed to Merck has been temporarily paused after some vaccinated volunteers experienced pain in their joints, a medical center in Geneva announced on Thursday.

But the center, University Hospitals of Geneva, said such reactions were common for vaccines, suggesting it did not think this represented a major setback to the development of the vaccine, which might become an important tool in containing the epidemic in West Africa.

The Merck vaccine is one of two that are in early testing in healthy volunteers at various sites around the world. The other is being developed by GlaxoSmithKline and the United States National Institutes of Health.

If the vaccines prove safe in these early tests and show evidence that they stimulate an immune system response, health authorities plan to conduct larger trials beginning next year in the African countries affected by the outbreak.

The vaccine being tested in Geneva was initially developed by the Public Health Agency of Canada and licensed to NewLink Genetics, a small biotechnology company in Iowa. Last month, NewLink licensed its rights to Merck, a company with far more resources and expertise in developing and manufacturing vaccines.

University Hospitals of Geneva said in a statement on Thursday that it had given the vaccine to 59 volunteers since Nov. 10 and that over all, the vaccine was “very well tolerated.” Some people got fever or muscle pain in the days and hours after the injection, but that was expected and the volunteers had been warned about it.

However, it said, four volunteers then reported mild pain in the joints of the hands and feet 10 to 15 days after the injection, something not expected. The hospital said it therefore decided to halt the injections until Jan. 5, so it could study the situation and update the information about expected side effects that it provides to volunteers.

Joint pain after vaccination “is a well-documented phenomenon which does not worry specialists,” it said. It added, “The temporary interruption of a clinical trial is a standard precautionary measure in such cases.”

The vaccine is also being tested in Canada, Germany and Gabon, and in the United States at the Walter Reed Army Institute of Research and at the National Institutes of Health. These other teams have not observed such inflammation, the Geneva hospital said.

Merck said that the side effect was seen in volunteers receiving a higher dose and that part of the goal for the study was to define the proper dose. It said it understood that the study would continue, using lower doses.

“These events have not been reported at any of the other clinical sites,” the company said in a statement. “It is not known at this time whether these events are related to the vaccine or not.”

Merck paid $30 million initially to NewLink for rights to the vaccine and owes another $20 million when the vaccine enters later-stage testing. Shares of NewLink were down about 5 percent Thursday afternoon.

So far, the GlaxoSmithKline vaccine does not appear to have caused any safety problems, authorities have said.

The two vaccines use different technical approaches. Both are made of viruses that are genetically engineered so that they make a protein from the Ebola virus. The Merck vaccine uses vesicular stomatitis virus, which can cause a mouth disease in livestock but rarely in people. The Glaxo vaccine uses a chimpanzee adenovirus, which causes a type of common cold in chimps but is not known to cause illness in people.

Safety is considered crucial for vaccines because they are typically given to large numbers of healthy people. Indeed, companies developing Ebola vaccines have been seeking some indemnity should side effects emerge once the vaccines are used for mass inoculations, especially since the vaccines are being developed on a crash schedule.

In related news, Gavi, the Vaccine Alliance, said it was committed to spending up to $300 million to buy up to 12 million courses of Ebola vaccine to immunize people in countries affected by the outbreak. It said it would act as soon as a vaccine was recommended for use by the World Health Organization.

Gavi, once known as the Global Alliance for Vaccines and Immunization, is a public-private partnership funded by various governments, companies and charities including the Bill and Melinda Gates Foundation.

A version of this article appears in print on , on Page B3 of the New York edition with the headline: Hospital Pauses Test of an Ebola Vaccine Licensed to Merck. Order Reprints | Today’s Paper | Subscribe